1. The effects on blood and faecal lipids of the addition of 15 g of either high- or low-methoxyl pectin to the habitual diets of ten healthy young adults have been studied.

2. Serum total cholesterol levels were reduced by a mean of 16% during consumption of low-methoxyl pectin and 18% during consumption of high-methoxyl pectin. High density lipoprotein cholesterol levels and triglyceride levels were unchanged.

3. There was no difference in faecal fat and steroid excretion between the two pectins.

4. The results suggest that it is the gel-forming properties of the pectins which are important in the cholesterol-lowering effect rather than differences in bile acid bindingdue to different methoxyl contents.

1. Some modifications to the erythrocyte glutathione reductase assay for riboflavin status are described.

2. Cusum analysis of results collected on a quality-control (QC) haemolysate, analysedseparately at the beginning and end of each batch of samples over a period of 20 weeks, suggested that the activation coefficient (AC) was higher at the end of a batch than at the beginning.

3. The higher AC was due to higher FAD-stimulated enzyme activities of the QC samples measured at the end of the day, by comparison with the beginning, and this suggested that the conditions of assay were not optimal.

4. The conditions required to achieve maximal coupling of FAD to glutathione reductase(NAD(P)H2: glutathione oxidoreductase; EC 1.6.4.2) were therefore examined and found to be 15 min at 35° by comparison with the 5–7 min incubation used by most workers.

5. Alternatively, where samples are prepared in batches, the enzyme and FAD should be pre-incubated in the reaction mixture for 2 h at 4° or 1 h at 25° before the standard incubation of 5 min at 35°.

6. Additionally, the use of cummulative sum (cusum) analysis on the QC results suggested that there was a slight deterioration of QC sample after 4-weeks storage. However, theQC results obtained, remained within 2 standard deviations of initial results over a 20-week period, suggesting that the deterioration was very slight.

1. The effect of heat treatment of bran on true zinc absorption was measured using an isotope-dilution technique. A bran-based breakfast cereal (heated to 204° for 40 min during manufacture) was incorporated into a semi-synthetic diet at a level of 180 g/kg, A parallel diet was formulated containing an identical weight of untreated bran from the same source plus other ingredients used to make the cereal.

2. Young male Wistar rats (mean weight 80 g) were injected intramuscularly with 65Zn to label body Zn. They were given the heat-treated- and untreated-bran diets for 9 d. During the last 6 d of this period Zn intakes and faecal and urinary Zn were measured in order to calculate apparent Zn retention. True Zn retention was measured by taking into account losses of Zn of endogenous origin (labelled with 65Zn), by measuring faecal and urinary 65Zn taking the mean specific radioactivity of Zn in kidneys and upper small intestine to represent specific radioactivity of endogenous origin.

3. Heat treatment of bran removed approximately one-third of the phytate, but this was not enough to improve Zn absorption from the diet. True Zn retention measured by isotope dilution was significantly higher (P < 0.02) than apparent Zn retention measured bv the conventional balance technique.

4. The hypothesis that a reduction in particle size of bran would improve mineral availability was tested by feeding coarse and milled bran (100 g/kg diet) in a semi-synthetic diet to rats and measuring true Fe and apparent Zn absorptions. The importance of phytate was also investigated by feedino a diet containing dephytinized bran.

5. Male Wistar rats (mean weight 172 g) were given diets containing coarse, milled or dephytinized bran for 9 d. Fe and Zn intakes were measured and faeces and urine collected for Fe and Zn analysis.

6. The mean (±SE) particle size of the bran was reduced on milling from 3.5 (± 1.8) to 0.2–0.5 mm. There were no differences in the fraction of Fe retained between the three groups. Particle size had a small effect on Zn retention which was marginally higher in rats on the milled-bran diet (0.126 (± 0.023)) than in those on the coarse-bran diet (0.087 (± 0.012)). Total removal of phytate had a greater effect and apparent Zn retention from the dephytinized-bran diet was significantly higher (0.182 (±0.027), P < 0.01).

1. Conventional (CV) rats were given a single oral dose of 1 or 2 g maltitol. Urine and faeces were collected during the following 24 h and their contents of maltitol and sorbitol were measured.

2. Very little of either substance appeared in the faeces but appreciable amounts of sorbitol found in the urine indicated that the maltitol had been hydrolysed.

3. Excretion of maltitol and sorbitol was compared in germ-free and CV rats given an oral dose of 2 g maltitol. Significantly less of both substances was recovered in the faeces of CV rats, but urinary excretion was similar in both environments.

4. Maltitol injected intravenously gave rise to only traces of sorbitol in the excreta. A dose of 250 mg was cleared almost completely from the circulation within 1 h.

5. It is concluded that maltitol is hydrolysed by animal tissues, either in the gut lumen before absorption or in the gut wall during absorption. Maltitol and sorbitol are also degraded by gut bacteria, mostly in sites distal to the main absorptive area. The contribution to the host's nutrition would depend on the extent to which the end-products of fermentation are absorbed from the colon.

1. The results from two studies are reported of the effects on mental performance of omitting breakfast. The objective of the first study was to compare the performances of schoolchildren who habitually ate or did not eat breakfast. In the second study the effectsof omitting breakfast by those accustomed to eating the morning meal were investigated.

2. Mental performance was assessed by two short-term memory tests (a simple cancellation test in which paired letters were marked on a page of random letters) and a memory-search test in which tines containing a group of specified fetters were marked, a series of numerical additions, and an attention-demanding test (in which specified statements had to be verified).

3. Neither study revealed differences attributable to the omission or consumption of breakfast.

1. Dietary phenolic cinnamic acids are hydrogenated in the side-chain, demethylated and dehydroxylated in the rumen and are responsible for the large urinary output of benzoic acid by ruminants.

2. Decarboxylation of phenolic acids to simple phenols is another reaction of the intestinal microflora and experiments were made to determine the extent of this reaction in the rumen of sheep.

3. In five experiments phenolic compounds, quinic acid or casein were infused into therumen or abomasum of sheep and increments in urinary outputs of phenolic acids and phenols determined by thin-layer and gas-liquid chromatography.

4. Production of phenols was almost exclusively confined to reactions in the rumen.

5. Rumen administration of phenolic benzoic or phenylacetic acids which contained a 4-hydroxy substituent yielded large increments in urinary phenol outputs. Other phenolic benzoic and phenylacetic acids were not decarboxytated. Rumen decarboxylation of 4-hydroxy-3-phenylpropionic acid did not occur and decarboxylation of 4-hydroxycinnamic acids was slight.

6. Nearly half the tyrosine content of rumen-administered casein was excreted as p-cresol, a decarboxylation product of 4-hydroxyphenylaceticacid, p-Cresol was the principal phenol found in sheepurine.

7. Catechol and phenol were consistently found in sheep urine samples and p-ethylphenol, resorcinol, quinol, 4-methylcatechol, orcinoland pyrogallol were also found when suitable precursors were infused to the rumen.

8. It is concluded that p-cresol is a rumen metabolite of tyrosine. The other phenols found are microbial metabolites of phenolic precursorswhich are either widely distributed in plants such as 4-hydroxybenzoic, protocatechuic andvanillic acids or of more limited distribution such as the orcinol glycosides of some Ericaceous plants.

1. Twenty pigs were given one of five diets containing 0.9–39.2 g nitrogen/kg dry matter (DM) during the period 13–27 d of age.

2. The pigs were fed hourly, from 22–27 d of age, with a diet sprayed with an indigestible marker, 103 Ru-labelled Tris (l,10-phenanthroline)-ruthenium (II) chloride. All pigs were slaughtered at 27 d of age.

3. Flows of endogenous N estimated by feeding the diet containing 0.9 g N/kg and by regression analysis using results from all diets, were similar.

4. Flows of endogenous N were: stomach 1.8. duodenum 4.5, jejunum 4.2, ileum 3.5, caecum 2.7, large intestine 2.6 and faeces 1.7 g/kg dm intake.

5. Values are given for the flow of endogenous amino acids to the ileum.

6. Of the DM, 70% was digested anterior to the duodenum and for N the value was 10%. The percentage of N digested anterior to the jejunum was 70.

1. The effect of supplementing barley diets with urea (U), extracted decorticated groundnut meal (GNM) or Peruvian fish meal (PFM) on plasma free amino acid concentrations in sheep have been examined and the first limiting amino acid has been indicated by measuring the changes in the concentration of the plasma essential amino acids (PEAA) during a rumen infusion of a volatile fatty acid (VFA) mixture.

2. Three wethers fitted with rumen and re-entrant duodenal cannulas were given isonitrogenous, isoenergetic diets containing (g/kg dry matter (DM)) U 20, GNM 106 or PFM 78, the crude protein (nitrogen × 6.25) contents being 139, 145 and 148 respectively. The sheep were fed hourly, the mean daily dm intake being 0.634 kg.

3. Plasma concentrations of valine, threonine, lysine, isoleucine and leucine were linearly related to their concentrations in duodenal digesta.

4. A VFA mixture was infused into the rumen for 6 h to supply (mmol/min) acetate 1.47, propionate 0.22 and n-butyrate 0.27. Blood samples were taken 6 h before, during and 12 h after the end of the infusion.

5. The concentration of all PEAA decreased relative to the pre-infusion and post-infusion controls but there were no significant differences between diets.

6. The mean decreases in concentration averaged over all three diets showed that the decrease in concentration of methionine (41.5%) was far greater than for any other essential amino acid suggesting that under these conditions methionine was the first limiting amino acid.

1. A total of six diets based on maize silage were formulated to examine the effect of protein- and non-protein-nitrogen, and energy supplementation on the flow of amino acids to the small intestine and the synthesis of microbial amino acids in the rumen of growing cattle. All diets contained 24 g totai nitrogen (N)/kg dry matter (DM), of which 550 g N/kg total N was supplied by either urea or fish meal. Four diets contained low levels of barley (estimated total dietary metabolizable energy content of 10·4 M J/kgDM) and urea-N and fish meal-N were supplied in the ratios 3:1, 1·4:1, 0·6:1 and 0·3:1. The other two diets contained between 300 and 400 g barley/kg total diet (11·3 MJ metabolizable energy/kg DM) and the urea-N to fish meal-N ratios were 3:1 and 0·3:1.

2. On the four low-energy diets, fish meal inclusion tended to reduce the extent of organic matter (OM) digestion in the rumen but significantly increased duodenal amino acid supply (P < 0·05) in a quadratic manner. Microbial-N synthesis was increased by the two intermediate levels of fish meal supplementation but declined at the highest level of inclusion. With increasing levels of fish meal inclusion, a greater proportion of the dietary protein was found to escape rumen degradation and the apparent degradabilities of fish meal and maize-silage protein of all four diets were estimated to be 0·22 and 0·73 respectively.

3. The substitution of barley for part of the maize silage enhanced duodenal supply of amino acids, irrespective of the form of the N supplement, and stimulated microbial amino acid synthesis. For all diets efficiency of microbial-N synthesis was found to vary between 22·5 and 46 g N/kg rumen-digested OM. Contrary to what was found for low-energy diets, the inclusion of fish meal tended to reduce the flow of dietary protein to the small intestine, but these differences were not statistically significant.

4. The results appertaining to microbial synthesis, dietary protein degradabilities and duodenal amino acid flow for all diets are discussed in relation to the Agricultural Research Council (1980) proposals for the protein requirements of ruminants, and the production responses observed when similar diets were fed to growing cattle.

1. Seven Friesian heifers in mid-lactation were used in an experiment to measure the effects of including casein, formaldehyde-treated casein or formaldehyde-treated soya-bean meal in the diet on performance and on the concentrations of certain metabolites and hormones in the blood.

2. Milk yield and the concentration of fat, protein and lactose in milk were not affected by the treatments.

3. The concentration of growth hormone (GH) in jugular venous blood was higher with both formaldehyde-treated proteins than it was with untreated casein (P < 0·05). Diet had no effect on insulin, prolactin or thyroxine concentrations in blood.

4. Urea concentration tended to be higher and non-esterified fatty acids lower in blood from heifers offered the diet containing untreated casein, but these differences were not statistically significant. Blood glucose concentration was not affected by dietary treatment.

5. It was concluded that blood GH concentration can be increased by offering protein supplements which will increase total amino acid supply to the intestines in lactating cattle. This appears to be a direct effect on GH status independent of effects on milk yield.

1. A combination of isotope-dilution and arteriovenous-difference techniques was used to determine the significance of ketones to energy homoeostasis in fasted pregnant ewes.

2. There was incomplete interconversion of D(−) 3-hydroxybutyrate (3HB) and acetoacetate (AcAc) and therefore neither entry rate nor oxidation of total ketone bodies could be estimated by assuming circulating ketone bodies represent a single metabolic compartment. Total ketone body metabolism was satisfactorily summarized using a three-compartment model. In fasted pregnant ewes the mean entry rate of total ketones was 1 mmol/h per kg body-weight and of the ketones entering the circulation 87% were promptly oxidized to carbon dioxide accounting for 30% of the total COa production.

3. Ketone bodies are readily utilized by hind-limb skeletal muscle such that if completely oxidized, 18±4 and 48±3% of the oxygen utilized could be accounted for in fed and fasted pregnant ewes respectively. For both 3HB and AcAc there was a hyperbolic relationship between utilization and arterial concentration. The apparent Michaelis constant (Km) values were 0·55 and 1–42 mM respectively and the maximum velocity (Vmax) 2·9 and 5·6 mmol/h per kg muscle. The arterial concentration of AcAc is always below the Km value and this limits the utilization rate. The D(−) 3HB concentration, however, may surpass that required for maximum utilization and ketoacidosis may be a consequence of this.

4. A two-compartment model was used to analyse ketone body metabolism by hind-limb skeletal muscle. The results suggested substantial intercon version and production of AcAc and 3HB.

5. The pregnant uterus utilized 3HB which if completely oxidized accounted for 12±2 (fed) and 25±4 (fasted) % of its O2 consumption. At least 64% of the net 3HB utilized was oxidized. AcAc was not utilized in significant quantities.

1. The nitrogen-sparing effect of methionine, methionine sulphoxide, homocystme, cystine and choline was studied in rats by determining daily N excretions during 5 d after changing from a high-protein diet to a protein-free diet, L-glutamic acid was used as a negative control.

2. L-, D- and DL-methionine were equally active in sparing N. L-methionine sulphoxide, DL-homocystine and L-cystine were as active as L-methionine. D-methionine sulphoxide was slightly less active than L-methionine sulphoxide, Choline hydrogen tartrate was not different from the negative control.

3. It is concluded that in short-term experiments cystine is the key substance in the N-sparing effect.

1. The effects of thyroid hormones on the range of tissue protein synthesis in growing pigs using the constant infusion technique with [14c]leucine and [14C]lysine were studied.

2. During a 6 h infusion, samples were taken from blood and, at the end of the infusion, from liver, pancreas, stomach, small and large intestines, kidney cortex, kidney medulla, muscle and skin.

3. Lower relative specific radioactivities of free leucine and lysine in several tissues were observed in the hormone-treated group than in the untreated one.

4. The range of protein synthesis rate and the daily amount of protein synthesized in tissues was higher in all tissues after application of thyroid hormones.

5. Assuming that the organs analysed represented 70% of the total trichloroacetic acid-precipitable protein of the pig, the estimated range of daily protein synthesis was 251–490 and 312–880 g in untreated and hormone-treated pigs respectively.